The present invention relates to an epoxy resin composition for encapsulating semiconductor elements, which composition is low in water absorption and has excellent soldering resistance, and to semiconductor devices using this resin composition for encapsulation.
Epoxy resin compositions (hereinafter referred to merely as resin compositions) have been developed and utilized for protecting semiconductor elements from mechanical and chemical actions. The matters required for these resin compositions in their practical applications vary according to the type of semiconductor elements to be encapsulated, the type of a semiconductor device comprising such encapsulated elements, the use environment and other factors.
Increase of surface-mounted semiconductor devices has called for the development of resin compositions with low water absorption, and a large variety of resin compositions suited for such use have been proposed.
Currently, with increasing seriousness of the environmental problems, request for resin compositions containing neither halogen compound nor antimony oxide has become very strong. In order to comply with such a request, resin compositions using various types of flame-retardants other than halogen compounds and antimony oxide, and resin compositions not using even such flame-retardants have been proposed. At present, however, there is available no encapsulating resin composition which can perfectly satisfy requirements for good moldability, low water absorption, high soldering resistance, etc.
The present invention is envisioned to provide an epoxy resin composition for semiconductor encapsulation having excellent moldability and flame retardancy, low water absorption and high soldering resistance, and semiconductor devices using this resin composition for encapsulation.
Specifically, the present invention pertains to an epoxy resin composition for semiconductor encapsulation comprising (A) an epoxy resin in which the proportion of carbon atoms of aromatic derivation to the whole carbon atoms in the epoxy resin is 70% or more, (B) a phenol resin in which the proportion of carbon atoms of aromatic derivation to the whole carbon atoms in the phenol resin is 70% or more and whose phenolic hydroxy equivalent is 140 to 300, (C) a curing accelerator, and (D) an inorganic filler whose content W (wt %) in the whole epoxy resin composition satisfies 88xe2x89xa6Wxe2x89xa694, characterized in that the combustion starting temperature in thermogravimetric analysis of the cured epoxy resin composition in the air atmosphere is 280xc2x0 C. or higher. The present invention also relates to an epoxy resin composition for semiconductor encapsulation comprising (A) an epoxy resin in which the proportion of carbon atoms of aromatic derivation to the whole carbon atoms in the epoxy resin is 70% or more, (B) a phenol resin in which the proportion of carbon atoms of aromatic derivation to the whole carbon atoms in the phenol resin is 70% or more and whose phenolic hydroxy equivalent is 140 to 300, (C) a curing accelerator, and (D) an inorganic filler whose content W (wt %) in the whole epoxy resin composition satisfies 88xe2x89xa6Wxe2x89xa694, characterized in that the retention A (wt %) of the cured product in thermogravimetric analysis of the cured epoxy resin composition in the air atmosphere satisfies W+[0.1xc3x97(100xe2x88x92W)]xe2x89xa6A.
In a more preferred embodiment of the present invention, there are provided the epoxy resin compositions as described above, in which the epoxy resin is the one represented by the following formula (1): 
wherein R1 to R4 are a hydrogen atom, a phenyl group or a methyl group and may be identical or different, or the one represented by the following formula (2): 
wherein R1 to R8 are a hydrogen atom, a methyl group or a tertiary butyl group and may be identical or different, and the phenol resin is the one presented by the following formula (3): 
wherein n is a mean value which is a positive number of 1 or greater, the one represented by the following formula (4): 
wherein R1 is a hydrogen atom or a methyl group, and n is a mean value which is a positive number of 1 or greater, or a resin produced by conducting polycondensation of a petroleum heavy oil, formaldehyde polycondensate and a phenol. It is also envisaged in the present invention to provide semiconductor devices comprising semiconductor elements encapsulated with the above-described resin compositions.